Let us briefly discuss the renormalization procedure.
The renormalization matrix of the operators in Eq. (REF ) has been known
for a long time [1]}, [2]}, [3]}, [4]}. Since the CFs \(C^{\perp \perp }_1\)  and
\(C^{\parallel \perp }_1\)  are non-zero already in the tree approximation, their proper
renormalization requires the knowledge of the \(Z\)  factors, \(Z_{{\perp \perp }}\)  and
\(Z_{{\parallel \perp }}\) , at three loops. Thus, the requirement of finiteness of the
CFs of the operator \( O_1\)  provides an alternative way for computing \(Z_{{\perp \perp }}\) 
and \(Z_{{\parallel \perp }}\) . From our results for the bare CFs, \((C^{\perp \perp }_{1})_B\)  and \((C^{\parallel \perp }_{1})_B\) , we
successfully construct the three-loop \(Z\)  factors, \(Z_{{\perp \perp }}\)  and \(Z_{{\parallel \perp }}\) ,
as well as the corresponding ADs. We also find full agreement with
the corresponding two-loop results, first computed in Ref. [5]}.
